Self-opening end closure having a repair coated rupturable interior score

ABSTRACT

A self-opening sheet metal end closure wherein a rupturable score is formed in the interior or product-facing surface of the end closure resulting in a highly cold worked residual of sheet metal located between the score and the exterior surface of the end closure, the end closure having a non-metallic repair coat with a concave cross-sectional structure provided on the rupturable score substantially within and only partially filling the void defined by the score. The repair coat structure substantially prolongs the resistance of the highly cold worked sheet metal residual to chemical attack by corrosive products contained in the container closed by the end closure, while the amount of force required to rupture the score during opening of the end closure is substantially unaffected by the presence of the repair coat.

United States Patent 1 Kinkel 1 May 29, 1973 [54] SELF-OPENING END CLOSURE Primary Examiner-George T. Hall HAVING A REPAIR COATED Attorney- Robert P. Auber, George P. Ziehmer and RUPTURABLE INTERIOR SCORE Josep Orlando [75] Inventor: Christian Frederick Kinkel,

Prospect Heights, Ill. [57] ABSTRACT A self-o enin sheet metal end closure wherein a rup- [73] Assgnee' Ainerican can Company Greenturable score is formed in the interior or product-facwich, Conn.

mg surface of the end closure resulting in a highly cold Filed! p 17, 1972 worked residual of sheet metal located between the [2!] Appl No: 244,667 score and the exterior surface of the end closure, the end closure having a non-metallic repair coat with a concave cross-sectional structure provided on the rup- U-S. "Inn-220,54, turable core substantially and only partially [51] Int. Cl. ..B65d 17/24 filling the void d f by the Score The repair Coat [58} Field of Search ..220/54, 27, 53 Structure Substantially prolongs the resistance of the I highly cold worked sheet metal residual to chemical [56] References m attack by corrosive products contained in the con- UNITED STATES PATENTS tainer closed by the end closure, while the amount of force required to rupture the score during opening of Kinkel'. the end closure is substantially unaffected the 3,610,462 10/1971 Saunders....

presence of the repair coat.

8 Claims, 5 Drawing Figures SELF-OPENING END CLOSURE HAVING A REPAIR COATED RUPTURABLE INTERIOR SCORE The present invention generally relates to self or easy opening end closures for containers and more particularly it relates to a repair coat structure for improving the resistance to corrosion of a rupturable score formed in the interior or product-facing surface of an end closure.

Various types of self-opening end closures having interior rupturable scores have been disclosed in recently granted United States Patents. See for example the U.S. Pats. to Lipske (No. 3,397,811, granted Aug. 20, l968), Saunders (No. 3,507,418, granted Apr. 21, 1970), Kennedy (No. 3,543,961, granted Dec. 1, 1970), and Wolfe (No. 3,563,199, granted Feb. 16, 1971).

The patents to Saunders both teach the repair of the interior rupturable score thereby providing increased corrosion resistance for the score by furnishing a repair coat on the score which covers the score completely. The repair coat taught by these two patents also cover the marginal areas of the interior surface of the end closureadjacent to the score and extend substantially beyond these areas.

It has been discovered that repair coats having the structure taught by these two aforementioned patents, while adequately protecting the rupturable score from corrosion, actually add significantly to the opening forces required to rupture the score duringthe opening of the end closure, since both the score residual metal and the heavy repair coat structure must be torn. In some cases, the opening forces are doubled as a result of this repair coat structure.

The present invention concerns a novel repair coat structure for the inside rupturable score which overcomes the above mentioned disadvantages of the prior art. This new repair coat, having a concave crosssectional structure,-is contained substantially within, and only partially fills, the void defined by the rupturable score. This repair coat structure substantially prolongs the resistance of the highly cold worked sheet metal residual of the rupturable score to chemical attack by corrosive products, while the amount of force required to rupture the score during opening of the end closure is substantially unaffected by the presence of the repair coat.

The present invention will be described and understood more readily when considered together with the accompanying drawings, in which;

FIG. 1 is a plan view of the interior surface of a selfopening end closure, made of either aluminum or tinfree steel sheet metal, having formed therein a rupturable score incorporating the novel repair coat structure of the present invention;

FIG. 2 is a plan view of the exterior surface of the self-opening end closure of FIG. 1;

FIG. 3 is an enlarged fragmentary cross-sectional view'of a rupturable score and non-rupturable score combination taken substantially along line 3-3 of FIG.

FIG. 4 is an enlarged fragmentary cross-sectional view of the rupturable, interior score with the repair coat thereon taken substantially along line 3-3 of FIG. 2; and

FIG. 5 is an enlarged fragmentary cross-sectional view of the rupturable, interior score with the repair coat thereon similar to FIG. 4 except that the end closure is made from tinplated steel.

Now referring to the drawings, a full panel, selfopening end closure, generally designated 10, embodying the instant invention is shown in FIGS. 1 and 2. The self-opening end closure 10 is made of sheet metal which may be either tin-free steel, tin-plated steel or aluminum, and, preferably, has a circular configuration. The self-opening end closure 10 includes a peripheral outwardly extending annular curled flange 12 which may be interfolded with an end flange of a container body (not shown) to form an end seam (not shown). The peripheral flange 12 merges into an annular countersink wall 14 which extends downwardly from the peripheral flange 12 to an imperforate central panel 16.

Rupturable score 18 and, if desired, non-rupturable score 20 are formed in the interior surface 22 of the central panel 16. The radially outer rupturable score 18 is positioned adjacent to the periphery of central panel 16 to define a large removable portion 24 within central panel 16 which becomes detached from the end closure 10 when the score 18 is completely ruptured. The radially inner, non-rupturable score 20 is positioned adjacent to the periphery of removable portion 24 inwardly from, and preferably substantially concentric with, rupturable score 18. As is clearly shown in FIG. 3, the non-rupturable residual sheet metal section 26 of the non-rupturable score 20 has a substantially greater thickness than the rupturable residual sheet metal section 28 of the rupturable score 18, the differential in the thickness preferably being within the range of approximately 0.0025 to 0.003 inch. The center-tocenter spacing between the rupturable score 18 and the non-rupturable score 20 is preferably within the range of approximately 0.060 to 0.080 inch. The nonrupturable score 20 functions to protect the rupturable score I8 from premature, inadvertent rupture in the manner described in U.S. Pat. No. 3,406,866, to Jasper, granted Oct. 22, 1968.

In order to provide means for rupturing the rupturable score 118 when desired, an opening tab 30 is fastened to removable portion 24 on the exterior surface 32 of the central panel at a location adjacent to exterior surface 34 of the rupturable residual sheet metal section 28 by a hollow rivet 36. Rivet 36 is integral with the removable portion 24 and has a peripheral portion 38 which overlies and bears down on opening tab 30 to secure it on the removable portion 24.

Opening tab 30 is provided with a handle portion 40 into which the finger of a user may be inserted and a nose portion 42 which will be urged downwardly into contact against the exterior surface 34 of the rupturable residual sheet metal section 28 when the user raises the handle portion 40 of opening tab 30 to initiate rupture of the rupturable residual sheet metal section 28. After handle portion 40 has been rocked upwardly and forwardly to a substantially vertical position in relation to the central panel 16 to thereby complete the initial rupture of the portion of residual section 28 adjacent to nose portion 42 of tab 30, the user exerts a pulling force upwardly and rearwardly ,in relation to central panel 16 to achieve the rupture of the remaining portion of the rupturable residual section 28 and detachment of the removable portion 24 from the remaining peripheral portion of the central panel 16.

As shown in FIG. 3, both the rupturable score 18 and the non-rupturable score 20 preferably have a generally trapezoidal cross-sectional profile. Rupturable score 18 defines a void in the interior surface 22 of central panel 16 which is bounded by two steeply inclined, and oppositely disposed, side walls 44 which convergently extend from the interior surface 22 of central panel 16 toward the exterior surface 32 of the panel 16. A substantially flat base wall 46, which is in a plane generally parallel to the interior surface 22 of the panel 16, connects with the converging edges of the respective side walls 44 at corners of intersection 48. The base wall 46 preferably has a width within the range of 0.0015 to 0.0035 inches. The non-rupturable score 20 has substantially the same structural features as the rupturable score 18 except for the above-described substantial difference between the thickness of the non-rupturable residual sheet metal section 26 and the thickness of the rupturable residual sheet metal section 28.

The rupturable score 18 in being formed in the interior surface 22 of central panel 16 acts as a notch which concentrates the applied stresses when rupturing of the rupturable residual sheet metal section 28 by means of pulling the opening tab 30 upwardly and rearwardly after the initial fracturing of the residual section 28. For that reason, the total work required to completely rupture the residual sheet metal section 28 of the interiorly-formed rupturable score 18 is greatly reduced from that required to completely rupture the residual section of an exteriorly-formed rupturable score having the same residual sheet metal thickness. This unique function of the interior rupturable score provides the advantage of ease of opening at a substantially greater score residual sheet metal thickness than attainable with the exterior rupturable score where the stresses are spread over a larger area of the interior surface of the residual section opposite to the outside rupturable score.

FIG. 4 illustrates the rupturable score 18 on a greatly enlarged scale as compared to that of FIG. 3. The interior and exterior surfaces, 22 and 32 respectively, of the self-opening end closure preferably have nonmetallic protective coatings, generally designated 50 and 52 respectively, applied thereto. At an initial stage in the manufacture of end closures, generally circular blanks are punched from a continuous web of sheet metal. Next, the blanks are converted into basic ends ordinarily having a flange portion, a countersink wall, and a flat central panel. Preferably the non-metallicprotective coatings are applied to the respective surfaces of the end closure 10 when the sheet metal is in the web form before the blank has been punched from the web of sheet metal. The protective coatings 50 and 52 may be applied to the opposing surfaces 22 and 32 by any suitable process, for example, by a conventional rolling or spraying process.

The double score combination of the end closure 10 is formed by a conventional double scoring tool which is impressed into the central panel 16 while the end closure 10 is supported on a suitable anvil.

The double scoring tool preferably has a crosssectional profile which is substantially complementary to the desired profiles of the double scores 18 and 20.

It can be readily understood that the protective coating 50, on the interior surface 22 of the end closure 10, is interrupted at the location of the rupturable score 18 by the initial penetration of the scoring tool during the formation of the rupturable score. Fracturing of the coating 50 also occurs during the formation of the nonrupturable score 20, however, the subsequent repair of this score does not affect the functioning of the selfopening end closure 10 since score 20 is nonrupturable. Therefore, the discussion hereafter will be directed only to the rupturable score 18. The side walls 44 of score 18, formed during the scoring operation, are left substantially free of the protective coating 50 while the flat base wall 46 has thereon the strip-like portion 54 of the protective coating 50.

A non-metallic repair coat, generally designated 56, is applied by any suitable process of application, for example, by a conventional electrocoating or spraying process, to the side walls 44 so as to connect the edges 58 of the protective coating 50, at the location of interruption of the protective coating, with the separate strip-like portion 54 of the protective coating 50 left on the score base wall 46. The repair coat 56 has a generally concave cross-sectional structure and is contained substantially within, but only partially fills, the void defined by the rupturable score 18 below the general plane of the protective coating 50 on the interior surface of the end closure 10. A repair coat having the aforementioned structure substantially prolongs the resistance of the highly cold worked residual sheet metal section 28 of the rupturable score 18 to chemical attack by corrosive products contained within the container (not shown) to which the end closure 10 is attached. The amount of force required to rupture the score 18 in order to detach the removable portion 24 from the central panel 16 is substantially unaffected by the presence of the repair coat 56 in the score 18. Ex amples of repair materials which may be utilized in an electrocoating process are acrylic resin coatings and their copolymers, epoxy ester coatings, and oil modified alkyd coatings. Examples of repair materials which may be utilized in a spraying process, although not inclusive, are thermosetting vinyl coatings, such as a coating comprised of vinyl chloridevinyl acetate copolymers plus a ureaformaldehyde or melamineformaldehyde resin plus an epoxy resin, epoxypolyamide coatings, modified epoxy coatings, and epoxy ester coatings. Preferably, a repair coating comprising vinyl chloride-vinyl acetate copolymer plus melamine-formaldehyde resin plus an epoxy resin is utilized in the spraying process.

FIG. 5 illustrates the rupturable score 18 on an enlarged scale substantially identical to the illustration in FIG. 4, but where the score 18 is formed on the interior surface 22 of an end closure made of tin-plated steel. In the case of tin-plated steel, the substrate of steel sheet metal has a layer of tin on its interior surface 22, and also, preferably, on its exterior surface 32. Each of the tin layers may have a weight within the range of approximately 0.25 pound/base box to 1.35 pound/base box. Preferably, the tin layer 60 on the interior surface 22 of the steel sheet metal has a weight of approximately 0.75 pound/base box, and the tin layer 62 on the exterior surface of the steel sheet metal has a weight of approximately 0.25 pound/base box.

As in the case of the non-metallic protective coatings 50, 52, the tin layers 60 and 62 are preferably applied to the steel sheet metal when the sheet is in the web form before the blank has been punched from the web of steel sheet metal. The tin layers 60 and 62 may be applied by any suitable process of application, for example, by a conventional electrodeposition or hotdipping process. The penetration of the scoring tool into the central end panel 16 during the formation of the rupturable score 18 results in the retention of the tin coating 60 on the side walls 44 at a weight within the range of approximately 40 to 70 percent of the original weight of the tin layer 60. This is due to the greater surface area of the score side walls 44 as compared to the original surface area of the interior surface 22 which has now been replaced by the score side walls.

Also, the scoring operation results in the retention of the tincoating 60 on the flat base wall 46 of the score 18 at substantially the same weight as the original weight of the tin layer 60 on the interior surface 22 at the end closure 10.

As in the description of FIG. 4, a repair coat 56 is applied to the score 18 of FIG. 5 in an identical manner thereby prolonging the resistance of the highly cold worked residual sheet metal section 28 of the tin-plated steel end closure.

The non-metallic repair coat 56, having the concave cross-sectional structure as illustrated in FIGS. 4 and 5, advantageously is located below the interior surface 22 of the end closure where it is less susceptible to damage in subsequent handling than those end closures having the repair coat structure taught in the aforementioned U.S. Pat. Nos. 3,397,811 and 3,507,418. Furthermore, the sheet metal surrounding the score 1%, which has the least amount of coverage by repair coat 56, is the metal nearest the outer edges of the side walls 44 which is in a relatively unworked state and which offers inherent corrosion resistance far superior to that of the highly cold worked sheet metal in the region of residual section 28.

The protective coatings 50 and 52 and the repair coat 56 may be any coatings that are non-harmful to, with the corrosive product against attack by the coated metal of the end closure and will also protect the covered metal against attack by the corrosive product packaged within the container.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the various parts thereof without departing from the spirit and scope of the invention or sacrificing any of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

What is claimed is:

l. In a self-opening end closure for a container adapted to contain corrosive products, said closure being made of sheet metal and having a rupturable score formed in the interior, product-facing surface of said closure, a highly cold worked residual of sheet metal located between the score and the exterior surface of said closure, and a non-metallic protective coating on at least the interior surface of said closure, said coating being interrupted at the locating of said rupturable score, wherein the improvement comprises:

a non-metallic repair coat of a concave crosssectional structure on said rupturable score substantially within, and only partially filling, the void defined by said score, whereby the resistance of said highly cold worked sheet metal residual to chemical attack by corrosive products contained within a container closed by said closure is substantially prolonged, while the amount of force required to rupture said score to open said closure is substantially unaffected by the presence of said repair coat on said score.

2. A self-opening end closure according to claim 1 wherein said end closure is made of a steel basis sheet metal.

3. A self-opening end closure according to claim 1 wherein said end closure is made of aluminum sheet metal.

4. In a self-opening end closure for a container adapted to contain corrosive products, said closure being made of sheet metal and having a central end panel, a rupturable score defining a removable portion within said end panel, said score being formed by two steeply inclined, and oppositely disposed, side walls formed within the interior surface of said panel convergently extending from the interior surface of said panel toward the exterior surface of said panel and a base wall formed within the interior surface of said panel connecting the converging edges of said side walls, a highly cold worked residual of sheet metal between said score base wall and the exterior surface of said panel, and a non-metallic protective coating on at least the interior surface of said panel, said protective coating being interrupted at the location of said rupturable score such that said score side walls are substantially free of said protective coating and said score base wall has thereon a strip-like portion of said protective coating being separated from the remainder of said protective coating on said panel, wherein the improvement comprises:

a non-metallic repair coat on said side walls connecting the edges of said protective coating at the location of interruption of said protective coating with said strip-like portion of said protective coating on said score base wall, said repair coat having a generally concave cross-sectional structure and being contained substantially within, but only partially filling, the void defined in said panel by said score below the panel of said protective coating on the interior surface of said panel,

whereby the resistance of the highly cold worked residual of sheet metal to chemical attack by corrosive products contained within a container closed by said closure is significantly prolonged, while the amount of force required to rupture said score in order to detach said removable portion from said panel of said closure is substantially unaffected by the presence of said repair coat on said score.

5. A self-opening end closure according to claim 4 wherein said end closure is made of a steel basis sheet metal having a layer of tin of a given weight thereon between said protective coating and at least the surface of said closure which encompasses the interior surface of said panel, said layer of tin further extending at a reduced weight along said side walls underlying said recent to percent of the given weight of said tin layer.

7. A self-opening end closure according to claim 4 wherein said end closure is made of a steel basis sheet metal.

8. A self-opening end closure according to claim 4 wherein said end closure is made of aluminum sheet metal. 

1. In a self-opening end closure for a container adapted to contain corrosive products, said closure being made of sheet metal and having a rupturable score formed in the interior, product-facing surface of said closure, a highly cold worked residual of sheet metal located between the score and the exterior surface of said closure, and a non-metallic protective coating on at least the interior surface of said closure, said coating being interrupted at the locating of said rupturable score, wherein the improvement comprises: a non-metallic repair coat of a concave cross-sectional structure on said rupturable score substantially within, and only partially filling, the void defined by said score, whereby the resistance of said highly cold worked sheet metal residual to chemical attack by corrosive products contained within a container closed by said closure is substantially prolonged, while the amount of force required to rupture said score to open said closure is substantially unaffected by the presence of said repair coat on said score.
 2. A self-opening end closure according to claim 1 wherein said end closure is made of a steel basis sheet metal.
 3. A self-opening end closure according to claim 1 wherein said end closure is made of aluminum sheet metal.
 4. In a self-opening end closure for a container adapted to contain corrosive products, said closure being made of sheet metal and having a central end panel, a rupturable score defining a removable portion within said end panel, said score being formed by two steeply inclined, and oppositely disposed, side walls formed within the interior surface of said panel convergently extending from the interior surface of said panel toward the exterior surface of said panel and a base wall formed within the interior surface of said panel connecting the converging edges of said side walls, a highly cold worked residual of sheet metal between said score base wall and the exterior surface of said panel, and a non-metallic protective coating on at least the interior surface of said panel, said protective coating being interrupted at the location of said rupturable score such that said score side walls are substantially free of said protective coating and said score base wall has thereon a strip-like portion of said protective coating being separated from the remainder of said protective coating on said panel, wherein the improvement comprises: a non-metallic repair coat on said side walls connecting the edges of said protective coating at the location of interruption of said protective coating with said strip-like portion of said protective coating on said score base wall, said repair coat having a generally concave cross-sectional structure and being contained substantially within, but only partially filling, the void defined in said panel by said score below the panel of said protective coating on the interior surface of said panel, whereby the resistance of the highly cold worked residual of sheet metal to chemical attack by corrosive products contained within a container closed by said closure is significantly prolonged, while the amount of force required to rupture said score in order to detach said removable portion from said panel of said closure is substantially unaffected by the presence of said repair coat on said score.
 5. A self-opening end closure according to claim 4 wherein said end closure is made of a steel basis sheet metal having a layer of tin of a given weight thereon between said protective coating and at least the surface of said closure which encompasses the interior surface of said panel, said layer of tin further extending at a reduced weight along said side walls underlying said repair coat and still further extending along said base wall at substantially said given weight underlying said strip-like protective coating portion.
 6. A self-opening end closure according to claim 5, wherein: the given weight of said tin layer is within the range of approximately 0.25 pound/base box to 1.35 pound/base box, and the reduced weight of said tin layer on said score side walls is within the range of approximately 40 percent to 70 percent of the given weight of said tin layer.
 7. A self-opening end closure according to claim 4 wherein said end closure is made of a steel basis sheet metal.
 8. A self-opening end closure according to claim 4 wherein said end closure is made of aluminum sheet metal. 